Vehicle Seat

ABSTRACT

Provided is a vehicle seat that detects an alertness level of the driver, urges the driver to be alert, and permits the transition from autonomous driving to manual driving when the driver is alert enough for the manual driving. A vehicle seat configured to be mounted on a vehicle provided with a vehicle control device that can be selectively switched from autonomous driving to manual driving comprises: a seat body configured to support a driver; a seat control unit configured to communicate with the vehicle control device; an alertness level sensor provided on the seat body for detecting an alertness level of the driver; and a rousing unit provided on the seat body for providing a stimulus for urging the driver to be roused, wherein the seat control unit is configured to detect the alertness level of the driver according to a signal from the alertness level sensor upon receiving a start signal that is produced by the vehicle control device when a transition from the autonomous driving to the manual driving is to be initiated, to activate the rousing unit when the alertness level is lower than a first alertness level threshold value, and to permit the vehicle control device to perform the transition from the autonomous driving to the manual driving when the alertness level is equal to or higher than the first alertness level threshold value.

TECHNICAL FIELD

The present invention relates to a vehicle seat mounted on a vehiclewhich is capable of autonomous driving.

BACKGROUND ART

In a known vehicle driving control system for a vehicle whichautomatically follows a preceding vehicle while the driver performs amanual steering operation, the driver's alertness level is detectedbased on the time change in the steering angle of the steering wheeloperated by the driver, and a warning is given to the driver when thealertness level of the driver falls below a predetermined level (seePatent Document 1, for instance). According to the vehicle drivingcontrol system disclosed in Patent Document 1, a prescribed number ofwarnings are issued to the driver in an attempt to rouse the driver, andif the driver's alertness level is still below the predetermined level,the adaptive cruising control is prohibited so that the driver'salertness may be regained, and the driver may be enabled to perform thesteering operation.

PRIOR ART DOCUMENT(S) Patent Document(s)

-   Patent Document 1: JPH06-171391 A

SUMMARY OF THE INVENTION Task to be Accomplished by the Invention

However, according the vehicle driving control system of Patent Document1, even after the prescribed number of warnings are issued, the drivermay still not be alert enough to properly operate the steering wheel. Inthe case of a vehicle capable of autonomous driving, it is necessary tocorrectly determine the driver's alertness level because the transitionfrom the autonomous driving to the manual driving while the driver isnot fully alert may be hazardous. In this conjunction, the vehicle seatmay be expected as a promising platform for accurately detecting thealertness of the driver since the vehicle seat is in physical contactwith the driver.

In view of such background, an object of the present invention is toprovide a vehicle seat that can detect an alertness level of the driver,and urge the driver to be alert enough for the transition fromautonomous driving to manual driving to be performed in a safe manner.

Means for Accomplishing the Task

To achieve the above object, a vehicle seat (1) configured to be mountedon a vehicle (3) provided with a vehicle control device (5) that can beselectively switched from autonomous driving to manual driving,comprises: a seat body (7) configured to support a driver; a seatcontrol unit (10) configured to communicate with the vehicle controldevice; an alertness level sensor (8) provided on the seat body fordetecting an alertness level of the driver; and a rousing unit (9)provided on the seat body for providing a stimulus for urging the driverto be roused; wherein the seat control unit is configured to detect thealertness level of the driver according to a signal from the alertnesslevel sensor upon receiving a start signal that is produced by thevehicle control device when a transition from the autonomous driving tothe manual driving is to be initiated, to activate the rousing unit whenthe alertness level is lower than a first alertness level thresholdvalue, and to permit the vehicle control device to perform thetransition from the autonomous driving to the manual driving when thealertness level is equal to or higher than the first alertness levelthreshold value.

According to this aspect, the transition to the manual driving ispermitted when the driver's alertness level has been raised to asufficiently high level, and therefore, the transition of the vehiclefrom the autonomous driving to the manual driving can be carried outsafely.

In the above aspect, preferably, the seat control unit is configured toprohibit the transition from the autonomous driving to the manualdriving by the vehicle control device and to keep the rousing unitactivated when the start signal is received as long as the alertnesslevel is lower than the first alertness level threshold value.

According to this aspect, when the alertness level of the driver isdetected and the detected alertness level is low, a stimulus is given tothe driver to rouse the driver and the transition from the autonomousdriving to the manual driving is prohibited, whereby the transition fromthe autonomous driving to the manual driving can be carried out safely.

In the above aspect, preferably, the seat control unit is configured tochange at least one of an intensity, a time duration, a cyclic periodand a timing of the stimulus in dependence on the alertness level.

According to this aspect, the stimulus for urging the driver to beroused can be given to the driver in an appropriate manner.

In the above aspect, preferably, the alertness level sensor includes atleast one of a pulse sensor (21), a respiration sensor (22) and apressure sensor (23) configured to detect a pressure distribution on asurface of the seat body opposing the driver.

According to this aspect, the alertness level of the driver can bedetected in an appropriate manner.

In the above aspect, preferably, the alertness level sensor includes abrainwave sensor (24) provided on a part of the seat body opposing ahead of the driver.

According to this aspect, the alertness level of the driver can bedetected in an appropriate manner.

In the above aspect, preferably, the seat control unit is configured tocompute a sleep level of the driver including a distinction between aREM sleep and a non-REM sleep based on an output from the alertnesslevel sensor when the alertness level is lower than a second alertnesslevel threshold value which is lower than the first alertness levelthreshold value, and to change the stimulus provided to the driveraccording to the computed sleep level.

According to this aspect, by giving a stimulus corresponding to thesleep level to the driver, the regaining of the alertness of the drivercan be facilitated.

In the above aspect, preferably, the seat control unit is configured toreceive a signal predicting a time of the transition from the autonomousdriving to the manual driving from the vehicle control device, and toactivate the rousing unit in advance of the predicted time of thetransition by a prescribed time period.

According to this aspect, an adequate time period for the driver to beroused can be ensured.

In the above aspect, preferably, the seat control unit is configured toforward a vehicle stop signal to the vehicle control device when theseat control unit detects that the alertness level has continued to bebelow the first alertness level threshold value for a prescribed timeperiod when the start signal is received.

According to this aspect, the vehicle can be stopped w % ben the drivercannot be expected to be brought alert enough for manual driving.

In the above aspect, preferably, the rousing unit includes at least oneof a light source (31) configured to irradiate light to the driver, avibration source (32) configured to provide vibration to the driver, asound source (33) configured to generate sound, a heat source (34)configured to heat or cool at least a part of the driver's body, and anelectrical stimulus generating source (35) configured to apply anelectrical stimulus to the driver.

According to this aspect, the stimulus for urging the driver to beroused can be given to the driver in an appropriate manner.

In the above aspect, preferably, the seat body is mounted on a vehiclebody so as to be moveable between an autonomous driving position and amanual driving position, a drive unit (50) for moving the seat bodybetween the autonomous driving position and the manual driving positionis provided between the seat body and the vehicle body, and the rousingunit is configured to cause the drive unit to move the seat body fromthe autonomous driving position to the manual driving position as thestimulus.

According to this aspect, by moving the seat to a position suitable forthe manual driving, the stimulus for urging the driver to be roused isgiven to the driver.

In the above aspect, preferably, the vehicle seat further includes anarmrest (61) which is moveable relative to the seat body, and therousing unit is configured to cause the armrest to move as the stimulus.

According to this aspect, the armrest can be brought to a positionsuitable for the manual driving, and the stimulus that urges the driverto regain alertness can be given to the driver by the movement of thearmrest.

In the above aspect, preferably, the seat body is mounted on the vehiclebody so as to be rotatable around a vertical axial line, and the seatcontrol unit is configured to allow the seat body to be rotated in theautonomous driving position and to place the seat body relative to thevehicle body to face forward in the manual driving position.

According to this aspect, the vehicle occupants can be seated to faceone another during the autonomous driving by moving the seat body.Further, at the time of transition to the manual driving, the seat bodyis moved to a position suitable for the manual driving, whereby thestimulus to urge the driver to be alert can be given to the driver.

Effect of the Invention

Owing to the structures mentioned above, it is possible to provide avehicle seat that can detect the alertness level of the driver and urgethe driver to be alert so that the vehicle can be safely transitionedfrom the autonomous driving to the manual driving.

In one aspect of the present invention, when the alertness level of thedriver is detected and the detected alertness level is low, a stimulusis given to the driver to rouse the driver the transition from theautonomous driving to the manual driving is prohibited, whereby thevehicle can be safely transitioned from the autonomous driving to themanual driving.

In one aspect of the present invention, the alertness level sensorincludes at least one of a pulse sensor, a respiration sensor and apressure sensor configured to detect a pressure distribution on asurface of the seat body opposing the driver, whereby the alertnesslevel of the driver can be detected in an appropriate manner.

In one aspect of the present invention, the alertness level sensorincludes a brainwave sensor provided on a part of the seat body opposinga head of the driver, whereby the alertness of the driver can bedetected in an appropriate manner.

In one aspect of the present invention, the seat control unit isconfigured to compute a sleep level of the driver including adistinction between a REM sleep and a non-REM sleep based on an outputfrom the alertness level sensor when the alertness level is lower than asecond alertness level threshold value which is lower than the firstalertness level threshold value, and to change the stimulus provided tothe driver according to the computed sleep level, whereby a stimuluscorresponding to the sleep level can be given to the driver, and theregaining of the alertness of the driver can be facilitated.

In one aspect of the present invention, the seat control unit isconfigured to receive a signal predicting a time of the transition fromthe autonomous driving to the manual driving from the vehicle controldevice, and to activate the rousing unit in advance of the predictedtime of the transition by a prescribed time period, whereby an adequatetime period required for the driver to be properly roused can beensured.

In one aspect of the present invention, the seat control unit isconfigured to forward a vehicle stop signal to the vehicle controldevice when the seat control unit detects that the alertness level hascontinued to be below the first alertness level threshold value for aprescribed time period when the start signal is received, whereby thevehicle can be stopped when the alertness level of the driver cannot beexpected to be adequately regained.

In one aspect of the present invention, the rousing unit includes atleast one of a light source configured to irradiate light to the driver,a vibration source configured to provide vibration to the driver, asound source configured to generate sound, a heat source configured toheat or cool at least a part of the driver's body, and an electricalstimulus generating source configured to apply an electrical stimulus tothe driver, whereby the stimulus for urging the driver to be roused canbe given to the driver in an appropriate manner.

In one aspect of the present invention, the seat body is mounted on avehicle body so as to be moveable between an autonomous driving positionand a manual driving position, a drive unit for moving the seat bodybetween the autonomous driving position and the manual driving positionis provided between the seat body and the vehicle body, and the rousingunit is configured to cause the drive unit to move the seat body fromthe autonomous driving position to the manual driving position as thestimulus, whereby the stimulus for urging the driver to be roused isgiven to the driver.

In one aspect of the present invention, the vehicle seat furtherincludes an armrest which is moveable relative to the seat body, and therousing unit is configured to cause the armrest to move as the stimulus,whereby the armrest can be brought to a position suitable for the manualdriving, and the stimulus that urges the driver to regain alertness canbe given to the driver by the movement of the armrest.

In one aspect of the present invention, the seat body is mounted on thevehicle body so as to be rotatable around a vertical axial line, and theseat control unit is configured to allow the seat body to be rotated inthe autonomous driving position and to place the seat body relative tothe vehicle body to face forward in the manual driving position, wherebythe vehicle occupants can be seated to face one other by moving the seatbody. Further, at the time of transition to the manual driving, the seatbody is moved to a position suitable for the manual driving, whereby thestimulus to urge the driver to be alert can be given to the driver.

BRIEF DESCRIPTION OF THE DRAWING(S)

FIG. 1 is a schematic view of a vehicle seat according to an embodimentof the present invention:

FIG. 2 is a flowchart of a driver monitoring process executed by a seatcontrol unit;

FIG. 3 is a flow chart of the details of a rousing process shown in FIG.2 :

FIG. 4 is a flowchart of a driver monitoring process according to asecond embodiment;

FIGS. 5A and 5B are schematic views of a vehicle seat of a thirdembodiment in an autonomous driving position and a manual drivingposition, respectively; and

FIG. 6 is a schematic view of the positioning of an armrest of a fourthembodiment in a raised position (solid lines) and a lowered position(broken lines).

MODE(S) FOR CARRYING OUT THE INVENTION

Four embodiments of a vehicle seat according to the present inventionare described in the following with reference to FIGS. 1 to 6 .

First Embodiment

A vehicle seat 1 according to the present invention seats a driver, andis mounted on a vehicle capable of autonomous driving as shown in FIG. 1. A lower part of the vehicle body 4 of the vehicle 3 is fitted with avehicle control device 5 that allows the vehicle 3 to transition fromautonomous driving to manual driving by determining the condition of thevehicle 3 and the condition of the surrounding environment. The vehiclecontrol device 5 consists of a central processing unit (CPU) providedwith memory and a communication port 6 for forwarding and receivingsignals, and is configured to issue a start signal from thecommunication port 6 when the transition from the autonomous driving tothe manual driving of the vehicle 3 is initiated. Furthermore, thevehicle control device 5 is configured to autonomously drive the vehicleto a prescribed safe area (such as a service area and a parking lot) andpark the vehicle when a vehicle stop signal is received via thecommunication port 6.

The vehicle seat 1 is provided with a seat body 7 that can be movedrelative to the vehicle body 4. The seat body 7 is provided with a seatcushion 11 that supports the driver's buttocks and thighs, a seatback 12that supports the driver's back, and a headrest 13 connected to an upperpart of the seatback 12 so as to be positioned behind the driver's head.

The vehicle seat 1 is provided with an alertness level sensor 8 that ispositioned on the seat body 7 to detect the driver's alertness level.The alertness level sensor 8 includes any one of a pulse sensor 21, arespiration sensor 22, a pressure sensor 23, and a brainwave sensor 24.The pulse sensor 21 is provided on the front surface of the seatback 12,and is preferably disposed at a position corresponding to the driver'sheart. The pulse sensor 21 may consist of a sensor that counts thenumber of heartbeats or pulses of the driver within a predetermined time(heart rate), and may be based on any type such as a contact type,optical type, and an electrocardiographic type. The respiration sensor22 may consist of a sensor that detects the respiration rate andrespiration depth of the driver. The respiration sensor 22 may beconfigured to detect a pressure applied by a part of the drivercorresponding to the driver's lung to the front surface of the seatback12, or to detect a movement of the driver's chest from changes in theelectrostatic capacitance of a pair sheet electrodes placed on the frontsurface of the seatback 12, but other types of respiration sensors mayalso be used. The pressure sensor 23 consists of a sensor for detectingthe driver's posture based on the pressure applied to the seat body 7.The pressure sensor 23 is provided in a planar shape, and is placed onthe surface of the seat cushion 11 and the seatback 12 opposing thedriver, and detects the posture of the driver by measuring the surfacedistribution of the pressure (pressure distribution) applied to the seatcushion 11 and the seatback 12 by the driver. The brainwave sensor 24includes a magnetic sensor provided on a part of the headrest 13opposing the driver's head to detect a magnetic signal associated withthe activity of the driver's brain cells, and obtain the driver'sbrainwave. By using the alertness level sensor 8 which may consist anyof these sensors, it is possible to appropriately detect the driver'salertness level.

The vehicle seat 1 includes a rousing unit 9 that is provided on theseat body 7 to apply a stimulus to the driver to improve the alertnessof the driver. The rousing unit 9 includes at least one of a lightsource 31, a vibration source 32, a sound source 33, a heat source 34,and an electrical stimulus generating source 35 provided on the seatbody 7. The light source 31 consists of a device that is provided on theseatback 12 or the headrest 13 to irradiate light onto the driver'shead, and may consist of a light such as an LED, for example. Thevibration source 32 consists of a device that is provided on the seatcushion 11 or the seatback 12 to transmit vibration to the driver, andmay consist of a vibration motor, for example. The sound source 33consists of a device that is provided on the seat body 7, morepreferably on the headrest 13, to emit sound toward the driver, and mayconsist of a loudspeaker, for example. The heat source 34 consists of adevice for heating or cooling a part of the driver's body. In thisembodiment, the heat source 34 is a heater or a Peltier device that isprovided on the headrest 13 to heat or cool the driver's head. Theelectrical stimulus generating source is a device including a pair ofelectrodes provided on the surface of the seat cushion 11 or theseatback 12 opposing the driver and capable of applying a predeterminedvoltage between the two electrodes so that an electric stimulus may beapplied to the driver. By using the light source 31, the vibrationsource 32, the sound source 33, the heat source 34, and the electricalstimulus generating source 35, a stimulus that urges the driver to bealert can be applied to the driver.

The vehicle seat 1 is provided with a seat control unit 10 which ismounted to the seat body 7 to control the vehicle control device 5, thealertness level sensor 8, and the rousing unit 9. The seat control unit10 consists of a central processing unit (CPU) that includes memory anda communication port 41, and is provided on the seat body 7, preferablyunder the seat cushion 11. The seat control unit 10 is configured tocommunicate with the vehicle control device 5 via a cable that connectsthe communication port 41 of the seat control unit 10 with thecommunication port 6 of the vehicle control device 5.

The seat control unit 10 executes a driver monitoring process shown inFIGS. 2 and 3 when the vehicle 3 is in the autonomous driving mode andis about to transition from the autonomous driving to the manualdriving. The details of the driver monitoring process are discussed inthe following with reference to FIGS. 2 and 3 .

In the first step of the driver monitoring process, the seat controlunit 10 determines if a start signal has been received from the vehiclecontrol device 5 (step ST1). If the start signal is not received, thedriver monitoring process is concluded. At this time, the vehicle 3 ismaintained in the autonomous driving mode. When the start signal isreceived, the program flow advances to step ST2.

In step ST2, the seat control unit 10 detects the driver's alertnesslevel based on the output of the alertness level sensor 8. The alertnesslevel is defined as a numerical value that is zero when the driver is ina deep sleep and increases as the driver's alertness rises. When thealertness level sensor 8 consists of the pulse sensor 21, the driver'sheart rate at the start of driving is compared with the heart rate ofthe driver at the current time so that the seat control unit 10determines the decrease in the driver's alertness level according to thedecrease in the heart rate. When the alertness level sensor 8 consistsof the respiration sensor 22, the driver's respiration rate at the startof driving is compared with the respiration rate of the driver at thecurrent time, and the seat control unit 10 determines the decrease inthe driver's alertness level according to the decrease in therespiration rate. When the alertness level sensor 8 consists of thepressure sensor 23, the seat control unit 10 may detect the posture ofthe driver based on the pressure distribution and compute the driver'salertness according to the detected posture. When the alertness levelsensor 8 consists of the brainwave sensor 24, the seat control unit 10may compute the driver's alertness according to the waveform of thedetected brainwave of the driver. The seat control unit 10 may determinethe alertness level of the driver according to two or more of the heartrate, the respiration rate, the pressure distribution and the brainwavethat are detected. Once the seat control unit 10 has detected thealertness level of the driver according to the output(s) of thealertness level sensor 8 such as the heart rate, the respiration rate,the pressure distribution and the brainwave, the seat control unit 10executes step ST3.

In step ST3, the seat control unit 10 determines if the driver'salertness level is equal to or higher than a first alertness levelthreshold value. The first alertness level threshold value may bedetermined as a value of the driver's alertness level when the driver isadequately fit to drive manually. When the alertness level is equal toor higher than the first alertness level threshold value, the seatcontrol unit 10 executes step ST4. When the alertness level is lowerthan the first alertness level threshold value, the seat control unit 10executes step ST5.

In step ST4, the seat control unit 10 transmits a transition permissionsignal to the vehicle control device 5. Upon receiving the transitionpermission signal, the vehicle control device 5 switches the vehicle 3from the autonomous driving to the manual driving. At this time, thedriver's alertness level is equal to or higher than the first alertnesslevel threshold value, and the driver is sufficiently alert so that thedriver can safely drive the vehicle 3 manually.

In step ST5, the seat control unit 10 executes a rousing process. Thedetails of the rousing process is described in the following withreference to FIG. 3 .

The seat control unit 10 determines if the alertness level is equal toor higher than a second alertness level threshold as the first step ofthe rousing process (step ST11). The second alertness level thresholdvalue may be determined as a value of the alertness level of the driverwhen the driver is in a sleep which may be either a REM sleep or anon-REM sleep. The seat control unit 10 executes step ST13 when thealertness level is equal to or higher than the second alertness levelthreshold value, and executes step ST12 when the alertness level islower than the second alertness level threshold value, and the driver isdetermined to be in sleep.

In step ST12, the seat control unit 10 computes the sleep levelindicating the depth of the sleep based on the output (heart rate,respiratory rate, pressure distribution, brainwave, etc.) of thealertness level sensor 8. For example, the sleep level may be 1 in caseof a REM sleep and 2 to 5 in case of a non-REM sleep depending on thedepth of sleep. When the sleep level is 5, it corresponds to a sleep ofdeepest kind. Upon completion of the computation of the sleep level, theseat control unit 10 executes step ST13.

In step ST13, the seat control unit 10 determines at least one of theintensity, the time duration, the time cycle, and the timing(stimulation parameters) of the stimulus generated from the rousing unit9 based on the alertness level and the sleep level that are detected.For example, the seat control unit 10 sets the intensity of thestimulation of the rousing unit 9 (for example, the light source 31) tobe inversely proportional to the alertness level, and when the sleeplevel is equal to or higher than a predetermined value, the stimulusparameters may be set so as to give a stimulus to the driver fromanother rousing unit 9 (for example, the vibration source 32).

When the setting of the stimulation parameters is completed, the seatcontrol unit 10 drives the rousing unit 9 based on the stimulationparameters and gives the driver a stimulus (step ST14). When the rousingunit 9 is not activated, the seat control unit 10 activates the rousingunit 9 to give a stimulus to the driver, and further records astimulation start time at which the stimulus is started to be given tothe driver. When the rousing unit 9 has already been activated, and thedriver has already been given a stimulus, the seat control unit 10 maychange the intensity, the time duration, the cyclic time, and timing ofthe stimulus generated from the rousing unit 9 based on the stimulationparameters as required. Upon completion of the application of thestimulus, the recording of the stimulation start time, and the changingof the stimulus, the seat control unit 10 executes step ST6 of thedriver monitoring process shown in FIG. 2 .

In step ST6, the seat control unit 10 computes a stimulation time period(a time period during which the driver is stimulated) which is given asthe difference between the current time and an alertness recoveringtime, and determines if the stimulation time period is equal to orgreater than a predetermined threshold time period. The threshold timeperiod is set based on the time period required for the driver in sleepto be roused by the rousing unit 9, and is set to about 1 minute in thepresent embodiment. When the stimulation time period lasts for thethreshold time period or more, it can be determined that the driver isnot likely to be roused by the rousing unit 9. When the seat controlunit determines that the stimulation time period is equal to or greaterthan the threshold time period, the seat control unit 10 transmits avehicle stop signal to the vehicle control device 5 (step ST7), andconcludes the driver monitoring process. When the stimulation timeperiod is shorter than the threshold time period, the process flowreturns to step ST2 to detect the driver's alertness level and performthe rousing process. When the stimulation time period is equal to orlonger than the threshold time period, the seat control unit 10transmits a vehicle stop signal with the result that the vehicle 3 ismoved to a safe place and parked therein. Therefore, even when thedriver is not going to be roused, the safety of the vehicle 3 can beensured.

The effect of the vehicle seat 1 according to the first embodimentconfigured as described above is discussed in the following. In stepST2, the driver's alertness level is detected, and a stimulus thatprompts the driver to be roused is given until the alertness levelbecomes equal to or higher than the first alertness level thresholdvalue. Therefore, when the driver is alert enough to perform the manualdriving, the transition permission signal is transmitted to the vehiclecontrol device 5 and the transition to the manual driving is permittedwith the result that the transition from the autonomous driving to themanual driving can be performed safely.

Since the transition permission signal is not transmitted to the vehiclecontrol device 5 as long as the alertness level of the driver is lowerthan the first alertness level threshold value, the transition to themanual driving is prohibited. Therefore, the transition to the manualdriving is not performed as long as the driver is not alert enough forthe manual driving, whereby the safety of the vehicle 3 can be ensured.

In step ST13, the seat control unit 10 changes the stimulation parameteraccording to the sleep level. Therefore, even when the driver is insleep, a stimulus corresponding to the sleep level can be applied to thedriver so that the driver can be roused in an appropriate manner.

Second Embodiment

The vehicle seat 1 according to the second embodiment differs from thevehicle seat 1 of the first embodiment in that the vehicle controldevice 5 transmits a start signal including information on the predictedtime for the transition from the autonomous driving to the manualdriving to the seat control unit 10, and steps ST21 and ST22 areprovided in place of step ST1 in the driver monitoring process as shownin FIG. 4 .

In step ST21, the seat control unit 10 determines if a start signalincluding information on the notification or prediction of the time forthe transition to the manual driving is received. If the start signalincluding the information on the predicted time for the transition isnot received, the driver monitoring process is concluded. When the startsignal including the information on the predicted time for thetransition is received, the process flow waits until a time pointpreceding the time for the transition by a prescribed time period (stepST22). The prescribed time period is set to be longer than the timeperiod required for the driver to become alert enough to perform themanual driving. When the time point preceding the predicted time for thetransition by the prescribed time period is reached, the seat controlunit 10 executes step ST2 and the subsequent steps, and when thedriver's alertness level is equal to or lower than the first alertnesslevel threshold value, a rousing process is executed to apply a stimulusto the driver to urge the driver to be alert.

In the vehicle seat 1 according to the second embodiment, even if asignificant time period is required for the driver to be roused, anadequate time period is ensured for the driver to become alert enoughbefore the transition to the manual driving takes place, whereby thedriver can be brought to an alertness level suitable for the manualdriving in a reliable manner.

Third Embodiment

The vehicle seat 1 of the third embodiment differs from the vehicle seat1 of the second embodiment in that the seat body 7 is moveable withrespect to the vehicle body 4, and the rousing unit 9 includes a driveunit 50 configured to move the seat body 7 with respect to the vehiclebody 4. As shown in FIGS. 5A and 5B, the seat body 7 is connected to thevehicle body 4 so as to be rotatable about an axial line X extending ina substantially vertical direction between a manual driving position(FIG. 5A) in which the seated driver faces forward and an autonomousdriving position (FIG. 5B) in which the seated driver faces backward soas to face the rear seat. When in the manual driving position, the seatbody 7 is placed such that the driver can grab the steering wheel 51 inan effortless manner, and the driver's foot can easily reach the pedal52 which may be an accelerator pedal or the like. The drive unit 50 isprovided between the seat body and the vehicle body 4, and by receivinga signal from the seat control unit 10, rotates the seat body 7 aboutthe axial line X with respect to the vehicle body 4 to move the seatbody 7 between the autonomous driving position and the manual drivingposition.

In the present embodiment, both the vehicle control device 5 and theseat control unit 10 are provided along the axial line X. By arrangingin this way, the stress applied to the wiring connecting the vehiclecontrol device 5 to the seat control unit 10 due to the rotation of theseat body 7 can be minimized.

In the third embodiment, the seat control unit 10 causes the drive unit50 to move the seat body 7 from the autonomous driving position to themanual driving position in the rousing process in step ST5 of the drivermonitoring process. The rotation of the seat body 7 gives the driver astimulus so as to urge the driver to be alert.

In the vehicle seat 1 according to the third embodiment, during theautonomous traveling, the seat body 7 can be moved to a position whichallows the occupants to face each other so that a relaxing space can becreated in the vehicle. Furthermore, when switching to the manualdriving, the seat body 7 is moved to a position suitable for the manualdriving so that the driver can receive a stimulus that urges the driverto be alert. For this reason, when switching to the manual driving, theoperation to rouse the driver and the movement of the seat body 7 can beperformed at the same time so that a separate operation for stimulatingthe driver to be alert is not required.

Fourth Embodiment

The seat body 7 of the vehicle seat 1 according to the fourth embodimentis provided with an armrest 61 which is attached to an inboard side wallof the seatback 12 at one end thereof so as to be rotatable around alaterally extending axial line with respect to the seat body 7, as shownin FIG. 6 . Furthermore, an armrest control unit 62 is provided betweenthe seatback 12 and the armrest 61 so as to control the rotation of thearmrest 61 relative to the seatback 12. The armrest control unit 62 isconnected to the seat control unit 10, and is configured to move thearmrest 61 between a raised position (solid line) extending forward anda lowered position (broken line) extending downward by receiving aprescribed signal. When the armrest 61 is in the raised position, thedrivers arm can be placed on the armrest 61, and therefore, the seatbody 7 is considered to be in the manual driving position suitable forthe manual driving. On the other hand, when the armrest 61 is in thelowered position, the driver can freely move the arm so that the seatbody 7 is considered to be in the autonomous driving position suitablefor the autonomous driving.

In the fourth embodiment, the seat control unit 10 causes the armrestcontrol unit 62 to move the armrest 61 from the lowered position to theraised position in the rousing process in step ST5 of the drivermonitoring process. Owing to the movement of the armrest 61, the seatbody 7 transitions from the autonomous driving position to the manualdriving position, and the driver is given a stimulus to be alert.Therefore, the movement of the armrest 61 and the rousing of the drivercan be performed at the same time.

The present invention has been described in terms of specificembodiments, but the present invention is not limited by suchembodiments, and various modifications are possible. The alertness levelof the driver was detected by using the alertness level sensor 8 in theforegoing embodiments, but other forms of biometric sensors fordetecting the fatigue level, body condition, etc. of the driver may alsobe used, instead of the alertness level sensor 8, so that the stimulusto be given to the driver may be varied depending on the fatigue level,body condition, etc. of the driver. It may be also possible to arrangesuch that a vehicle stop signal is issued when an abnormalcardiovascular condition such as a cardiac arrest of the driver isdetected. In such a case, the seat control unit 10 may be configured tocontrol the electrical stimulus generating source 35 so as to provide asuitable electric stimulus for the driver's heart to beat with a properrhythm.

In the foregoing embodiments, the seat control unit 10 was provided inthe seat body 7, but the present invention is not limited by suchembodiments. For instance, the seat control unit 10 may be provided onthe vehicle body 4 integrally with the vehicle control device 5.

In the fourth embodiment, the armrest 61 was rotatably connected to theseatback 12, but the present invention is not limited by thisembodiment, and any other forms of armrest 61 can be used as long as thearmrest 61 is movably connected to the seatback 12.

Glossary of Terms

 1: vehicle seat  2: driver  3: vehicle  4: vehicle body  5: vehiclecontrol device  7: seat body  8: alertness level sensor  9: rousing unit10: seat control unit 21: pulse sensor 22: respiration sensor 23:pressure sensor 24: brainwave sensor 31: light source 32: vibrationsource 33: sound source 34: heat source 35: electrical stimulusgenerating source 50: drive unit 61: armrest 62: armrest control unit

1. A vehicle seat configured to be mounted on a vehicle provided with avehicle control device that can be selectively switched from autonomousdriving to manual driving, comprising: a seat body configured to supporta driver; a seat control unit configured to communicate with the vehiclecontrol device; an alertness level sensor provided on the seat body fordetecting an alertness level of the driver; and a rousing unit providedon the seat body for providing a stimulus for urging the driver to beroused; wherein the seat body is provided with a seat cushion thatsupports the driver's buttocks and thighs, a seatback that supports thedriver's back, and a headrest connected to an upper part of the seatbackso as to be positioned behind the driver's head, and wherein the rousingunit includes at least one of a light source configured to irradiatelight to the driver, a vibration source configured to provide vibrationto the driver, a sound source configured to generate sound, a heatsource configured to heat or cool at least a part of the driver's body,and an electrical stimulus generating source configured to apply anelectrical stimulus to the driver. 2-12. (canceled)
 13. The vehicle seataccording to claim 1, wherein the rousing unit includes the light sourceconsisting of a device that is provided on the seatback or the headrestto irradiate light onto the driver's head.
 14. The vehicle seataccording to claim 1, wherein the rousing unit includes the sound sourceconsisting of a device that is provided on the headrest to emit soundtoward the driver.
 15. The vehicle seat according to claim 1, whereinthe rousing unit includes the heat source consisting of a deviceprovided on the headrest to heat or cool a part of the driver's body.16. The vehicle seat according to claim 1, wherein the seat control unitis configured to detect the alertness level of the driver according to asignal from the alertness level sensor upon receiving a start signalthat is produced by the vehicle control device when a transition fromthe autonomous driving to the manual driving is to be initiated, toactivate the rousing unit when the alertness level is lower than a firstalertness level threshold value, and to permit the vehicle controldevice to perform the transition from the autonomous driving to themanual driving when the alertness level is equal to or higher than thefirst alertness level threshold value.
 17. The vehicle seat according toclaim 1, wherein the seat control unit transmits a vehicle stop signalwith the result that the vehicle is moved to a safe place and parkedtherein when the stimulation time period is equal to or longer than thethreshold time period.
 18. A vehicle seat configured to be mounted on avehicle provided with a vehicle control device that can be selectivelyswitched from autonomous driving to manual driving, comprising: a seatbody configured to support a driver; a seat control unit configured tocommunicate with the vehicle control device; an alertness level sensorprovided on the seat body for detecting an alertness level of thedriver; and a rousing unit provided on the seat body for providing astimulus for urging the driver to be roused; wherein the seat body isprovided with a seat cushion that supports the driver's buttocks andthighs, a seatback that supports the driver's back, wherein thealertness level sensor comprises a pressure sensor configured to detecta pressure distribution on a surface of the seat body opposing thedriver thereof, wherein the rousing unit includes at least one of alight source configured to irradiate light to the driver, a vibrationsource configured to provide vibration to the driver, a sound sourceconfigured to generate sound, a heat source configured to heat or coolat least a part of the driver's body, and an electrical stimulusgenerating source configured to apply an electrical stimulus to thedrive, and wherein the seat control unit detects the posture of thedriver based on the pressure distribution and detects the driver'salertness according to the detected posture thereof.
 19. The vehicleseat according to claim 18, wherein the seat control unit is configuredto detect the alertness level of the driver according to a signal fromthe alertness level sensor upon receiving a start signal that isproduced by the vehicle control device when a transition from theautonomous driving to the manual driving is to be initiated, to activatethe rousing unit when the alertness level is lower than a firstalertness level threshold value, and to permit the vehicle controldevice to perform the transition from the autonomous driving to themanual driving when the alertness level is equal to or higher than thefirst alertness level threshold value.
 20. The vehicle seat according toclaim 18, wherein the seat control unit transmits a vehicle stop signalwith the result that the vehicle is moved to a safe place and parkedtherein when the stimulation time period is equal to or longer than thethreshold time period.
 21. The manufacturing method of a vehicle seatcomprising: a step to prepare a seat body provided with a seat cushion,a seatback, and a headrest connected to an upper part of the seatback, astep to provide an alertness sensor on the seat body, a step to providea rousing unit on the seat body, and a step to connect the alertnesssensor and the rousing unit via a cable to a seat control unitconfigured to communicate with a vehicle control device performing atransition from the autonomous driving to the manual driving, whereinthe rousing unit includes at least one of a light source configured toirradiate light to the driver, a vibration source configured to providevibration to the driver, a sound source configured to generate sound, aheat source configured to heat or cool at least a part of the driver'sbody, and an electrical stimulus generating source configured to applyan electrical stimulus to the driver.